Twin-chip-mounting type diode

ABSTRACT

The present invention provides a diode that does not deteriorate its function even if it is used in an environment where the temperature change is considerable, such as in a terminal box for solar cell panel that is placed outdoors. A diode of twin-chip-mounting type in which each chip has a lead foot for being joined to a common terminal plate, wherein said lead feet are electrically connected with each other in a region of each lead foot from each chip to a portion wherein each lead foot is joined. The electrical connection of the lead feet is preferably formed by integral molding with each lead foot.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a twin-chip-mounting type diode thatcan ensure the performance even when a defect is generated in a joiningportion of a lead foot by deformation of a terminal plate due totemperature change. In particular, the diode of the present invention issuitable for use in a terminal plate circuit within a terminal box forsolar cell panel that is used in an environment where the temperaturechange is considerable.

BACKGROUND ART

Generally, in order to allow a diode to perform its function within acircuit, electrical connection is established by joining the lead footof the diode to a terminal plate.

Electrical connection between the diode and the terminal plate is firmin a general use. However, in a terminal plate that is placed within aterminal box for solar cell panel, the terminal plate is used in anenvironment where the temperature change is considerable, so that theexpansion and contraction of the terminal plate in a plane direction ofthe terminal plate occur frequently. This leads to a problem such thatthe joining part of the lead foot of the diode to the terminal platecannot withstand the expansion or contraction and generates cracks,whereby the joining part is easily exfoliated.

In particular, in a terminal box for solar cell panel having a terminalplate that is enlarged for improvement of the effect of dissipating theheat of the diode, such as disclosed in Japanese Patent ApplicationLaid-Open No. 2005-251962, the expansion and contraction of the terminalplate in a plane direction of the terminal plate are greatly transmittedto the joining part that joins the lead foot of the diode to theterminal plate, whereby the aforementioned problem has beenconspicuously raised. Therefore, a method has been demanded in which thediode can be allowed to perform its function in a highly reliable stateeven in such an environment.

DISCLOSURE OF THE INVENTION Problem that the Invention is to Solve

The present invention has been devised in view of the abovecircumstances of the prior art, and an object thereof is to provide adiode that does not deteriorate its function even if it is used in anenvironment where the temperature change is considerable, such as in aterminal box for solar cell panel that is placed outdoors, a terminalplate circuit having the diode joined thereto, and a terminal box forsolar cell panel including the terminal plate circuit.

Means for Solving the Problem

The present inventors have made eager studies in order to achieve theaforementioned object, and have found out that, even when a defect isgenerated in a joining part of one lead foot in a twin-chip-mountingtype diode having two lead feet connected to the same pole, one of thechips can perform its function, and that even if such a defect isgenerated, the two chips in the diode can be allowed to perform theirfunction by electrically connecting the lead feet with each other in aregion of each lead foot from each chip to a portion wherein each leadfoot is joined, thereby completing the present invention.

That is, the present invention is a diode of twin-chip-mounting type inwhich each chip has a lead foot for being joined to a common terminalplate, wherein said lead feet are electrically connected with each otherin a region of each lead foot from each chip to a portion wherein eachlead food is joined. In a preferred embodiment of a diode of the presentinvention, the electrical connection of the lead feet is formed byintegral molding with each lead foot.

Also, the present invention is a terminal plate circuit including theaforementioned diode and a terminal plate, where each lead foot of thediode is joined to a common terminal plate. In a preferred embodiment ofthe terminal plate circuit of the present invention, the terminal plateis enlarged so that the heat generated from the diode can besufficiently dissipated.

Furthermore, the present invention is a terminal box for solar cellpanel including the aforementioned terminal plate circuit.

Advantages of the Invention

Since the diode of the present invention is a twin-chip-mounting typehaving a special construction, the function thereof can be safelyensured without deteriorating the performance thereof even when a defectis generated at a joining portion of one lead foot. Further, even when adefect is generated in one chip besides the joining portion of one leadfoot, the function thereof can be safely ensured. In particular, thediode of the present invention is especially suitable for use in aterminal plate circuit within a terminal box for solar cell panel thatis used in an environment where the temperature change is considerable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically illustrating a conventionaltwin-chip-mounting type diode while omitting illustration of a coveringinsulating resin.

FIG. 2 is a view schematically illustrating an example of thetwin-chip-mounting type diode of the present invention while omittingillustration of a covering insulating resin.

FIG. 3 is a view schematically illustrating an example of thetwin-chip-mounting type diode of the present invention while omittingillustration of a covering insulating resin.

FIG. 4 is a view schematically illustrating an example of thetwin-chip-mounting type diode of the present invention while omittingillustration of a covering insulating resin.

FIG. 5( a) is a view schematically illustrating an example of thetwin-chip-mounting type diode of the present invention while omittingillustration of a covering insulating resin.

FIG. 5( b) is a view schematically illustrating an example of thetwin-chip-mounting type diode of the present invention without omittingillustration of a covering insulating resin.

FIG. 6( a) is a view schematically illustrating an example of thetwin-chip-mounting type diode of the present invention while omittingillustration of a covering insulating resin.

FIG. 6( b) is a view schematically illustrating an example of thetwin-chip-mounting type diode of the present invention without omittingillustration of a covering insulating resin.

BEST MODE FOR CARRYING OUT THE INVENTION

A diode of the present invention is a twin-chip-mounting type diode inwhich two chips are mounted, and each of these chips has a lead foot forbeing connected to a common terminal plate. The reason why thetwin-chip-mounting type diode is adopted is for coping with the defectof the chip by two chips and for coping with the defect of the joiningportion of the lead foot by two lead feet, and is a result of searchingfor a diode having a plurality of lead feet that can be connected to thesame pole. Therefore, unlike the typical method of using atwin-chip-mounting type diode, each lead foot of the diode of thepresent invention is used by being joined to the common terminal plateof the same pole.

The characteristic features of the twin-chip-mounting type diode of thepresent invention lies in that the lead feet are electrically connectedwith each other in a region of each lead foot from each chip to aportion wherein each lead foot is joined. The joining of the lead feetto the terminal plate can be carried out by a conventionally knownmethod, and can be carried out, for example, by soldering, welding,mechanical coupling (clamping or the like), or combination of solderingand mechanical coupling.

As illustrated in the schematic view of FIG. 1 omitting the illustrationof a covering insulating resin, the conventional twin-chip-mounting typediode is adapted in such a manner that two chips are independentlymounted on a frame, and an inner lead foot and an outer lead foot aredrawn out independently from each chip, and the tip end of the outerlead foot is joined to the terminal plate. Therefore, when a defect isgenerated at the joining portion of one outer lead foot, only one chipfunctions because the joining portion of the other outer lead footremains alive and the function of the diode is exhibited by the only onechip. This is not satisfactory in terms of the performance.

In contrast, in the twin-chip-mounting type diode of the presentinvention, as illustrated, for example, in the schematic view of FIG. 2omitting the illustration of a covering insulating resin, while an innerlead foot and an outer lead foot are drawn out independently from eachof the two chips that are independently mounted on a frame in a similarmanner and the tip end of the outer lead foot is joined to the terminalplate, the inner lead feet that have been drawn out from the two chipsare integrally molded so as to be electrically connected with eachother. Therefore, even when a defect is generated at the joining portionof one outer lead foot, an electric current can flow via the other outerlead foot and via the other inner lead foot to the inner lead foot ofthe side where the defect has been generated, so that the two chipsfunction effectively, and no problem is raised in terms of theperformance.

In FIG. 2, the electrical connection of the lead feet is achievedbetween the inner lead feet. However, in the present invention, as shownin the schematic view of FIG. 3, the electrical connection may beachieved between the outer lead feet. Alternatively, as shown in theschematic view of FIG. 4, the portion of the inner lead foot may beconstructed with wire bonding. Still alternatively, as shown in theschematic views of FIGS. 5 and 6, the lead foot need not be formed fromseparately-divided parts such as the inner lead foot and the outer leadfoot (see FIGS. 5( a) and 6(a)). Also, after a covering insulating resinis applied, the electrical connection between the lead feet may be seenfrom the outside (see FIG. 5( b)) or may not be seen from the outside(see FIG. 6( b)). In summary, what is required is that the lead feet areelectrically connected with each other in a region of each lead footfrom each chip to a portion wherein each lead foot is joined, and thateven when a defect is generated at the joining portion of one lead foot,the electric current from the terminal plate can be transmitted to bothof the chips via the other lead foot.

By joining the lead feet of the diode of the present invention to acommon terminal plate, a terminal plate circuit can be constructed. Atthis time, the terminal plate can be enlarged so as to sufficientlydissipate the heat generated from the diode. The terminal plate circuitformed in this manner exhibits advantageous effects particularly bybeing incorporated into a terminal box for solar cell panel that is usedin an environment where the temperature change is considerable.

INDUSTRIAL APPLICABILITY

The diode of the present invention is fabricated so as to functionsufficiently even when a defect is generated at the joining portionbetween the terminal plate and the lead foot in an environment where thetemperature change is considerable, so that it is extremely useful in asevere environment of use such as a terminal plate circuit within aterminal box for solar cell panel.

1. A diode of twin-chip-mounting type in which two chips are mounted onone frame and each of these chips has a lead foot and each lead foot isto be joined to a common terminal plate of the same pole, wherein saidlead feet are electrically connected with each other in a region of eachlead foot from each chip to a portion wherein each lead foot is joined,so that, even when a defect is generated at the joining portion of onelead foot to the terminal plate, the electric current from the terminalplate is transmitted to both of the chips via the other lead foot. 2.The diode according to claim 1, wherein the electrical connection of thelead feet is formed by integral molding with each lead foot.
 3. Aterminal plate circuit including the diode according to claim 1 and aterminal plate, wherein each lead foot of the diode is joined to acommon terminal plate of the same pole, and wherein, even when a defectis generated at the joining portion of one lead foot to the terminalplate, the electric current from the terminal plate is transmitted toboth of the chips via the other lead foot.
 4. The terminal plate circuitaccording to claim 3, wherein the terminal plate is enlarged so that theheat generated from the diode can be sufficiently dissipated. 5.(canceled)
 6. A terminal plate circuit including the diode according toclaim 2 and a terminal plate, wherein each lead foot of the diode isjoined to a common terminal plate of the same pole, and wherein, evenwhen a defect is generated at the joining portion of one lead foot tothe terminal plate, the electric current from the terminal plate istransmitted to both of the chips via the other lead foot.
 7. Theterminal plate circuit according to claim 6, wherein the terminal plateis enlarged so that the heat generated from the diode can besufficiently dissipated.
 8. A terminal box for solar cell panelincluding the terminal plate circuit according to any one of claims 3,4, 6 and 7.